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In Reply to: RE: Other thoughts posted by airtime on December 07, 2015 at 08:22:36
Just so everyone is on the same page, my speakers are based on the concept of the Dynaco A25's where the 10" woofer rolls off naturally and smoothly on its own, and needs no low pass filter. The tweeter is then blended in with just a simple first order high pass filter. I have two pair built like that using SEAS woofers and SEAS tweeters in existing cabinets.
The primary pair is built in some custom made Advent replica cabinets that have nicer veneer, are mirror imaged, and internally braced. That pair is Acoustic Suspension and uses the SEAS A26RE4 woofer with a 0.5 ohm series R to get the bass Q I wanted and extend the low bass a few more Hz. Fb is about 44 Hz and the bass Q was set to 0.85. The woofer and tweeter were adapted to use the existing screw holes, so original Advent or New Advent drivers can be reinstalled. The second pair are built in JBL L-110 cabinets, and the woofer there is the SEAS 25F-EW in a coated cone version. That's the replacement woofer for the A25. The cabinet is ported, and about 75% filled with Acousta-stuf. In room, the bass extends to below 30 Hz.
The tweeters (SEAS 27TBFC/G) are the same in both, as is the crossover which consists of a 10 uF film capacitor and an 8 ohm L-pad in series with the tweeter.
So the sound is much like the A25 in the midrange; but with tighter bass, better dispersion in the highs, and a somewhat more open and clearer sound overall. The highs are very smooth and have what I call a non-bright quality. With the right electronics, there is no edge, no false brightness, none of the over-etched quality of many speakers, and the integration is perfect. Imaging is very good. And since the drivers and crossovers are all new components, and with rubber surrounds on the woofers, they will outlive me.
To complement the speakers, I need electronics that do not have an edgy or gritty quality, tight bass, and no false brightness. The Rotel Stack with the RTC-940AX tuner-preamp, RCD-971 CD player, and the RB-1050 dual mono power amp works wonderfully well with the speakers.
I have three other amps, an NAD C350, an NAD C320BEE, and the Onkyo TX870 receiver. Both NAD's are integrated amps. As a match to the speakers, the C320BEE is closest to the Rotel gear; as it has the smoothness and non-brightness, and images very well. The bass, however, is not quite as tight as I'd like. The TX-870 is next in line, and a little of the naturalness escapes; although the bass is very powerful and solid. The C350 finishes in 4th place because it has a little false brightness and edge, and has a narrower soundstage. The bass is very solid. There's also a second Rotel CD player, the RCD-955AX. It is sensitive to interconnects and with a 12" long 25 pF cable sounds exactly like the RCD-971. But use a 1 meter cable and it picks up a hard, bright edge.
My goal at this point is to maintain the sound I have with reliable gear.
Jerry
Follow Ups:
As a match to the speakers, the C320BEE is closest to the Rotel gear; as it has the smoothness and non-brightness, and images very well. The bass, however, is not quite as tight as I'd like.
I think you'll find the C350 also has a proportionally stiffer power supply (~50 joules vs. 32) which may account for differences in bass impact.
Right on! 33% larger filter caps, a larger toroidal transformer and higher rail voltages. Continuous power at clipping is pretty close; but the C350 has significantly higher dynamic power ratings.
The topology of both is very similar, including passive interstage tone controls.
Jerry
As you are well aware, rail voltage has a greater effect on energy storage and is reflected in the figures I quoted.
While my Audio Research preamp has but 940 uF of capacitance, its rail runs 285V resulting in 38 joules of storage - more than many 100 watt amplifiers.
The flagship REF10 linestage is dual mono with well over 200 joules!
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